Diseases of the central nervous system (CNS) include many of the most devastating and burdensome of all human illnesses. Despite their ubiquity and impact, diseases of the nervous system remain among the most poorly treated. New CNS drugs are needed, but the complexity of the nervous system has largely made CNS drug discovery refractory to reductionist and in vitro approaches. For this reason, most existing CNS drugs were discovered by serendipitous observation of behavioral effects in living animals, not by in vitro screening. We propose to use high-throughput behavioral assays as a means of screening for novel neuroactive drugs. We have developed a fully-automated system capable of tracking and quantifying zebrafish behaviors in high- throughput, 96-well format. Psychotropic drugs from specific functional classes produce distinct behavioral profiles in this assay, suggesting a strong correlation between zebrafish behavioral profiles and small molecule mechanism of action. We aim to use a training set of 800 known neuroactive drugs and specific genetic perturbations to test and validate the assay. A screen of 50,000 small molecules will then identify novel neuroactive compounds that create behavioral profiles matching those of known psychotropic drugs in the training set. The zebrafish assay we have developed is the first high-throughput screen capable of assessing behavioral effects of small molecules in a vertebrate. Because the zebrafish behavior integrates inputs from several major neurotransmitter systems, the assay can be used to identify compounds that act on the CNS through diverse mechanisms. The extensive training set of 800 psychotropic drugs we are using enables careful validation of the assay and provides a powerful means of assigning potential mechanisms of action for novel compounds discovered. Successful completion of this project will create a robust and flexible system for discovering neuroactive compounds. It will also lead directly to discovery of novel lead compounds that may be developed further for treating nervous system disorders. PUBLIC HEALTH RELEVANCE: Discovering new treatments for diseases of the nervous system has been difficult because of the brain's complexity and the resulting need to test drug candidates in difficult animal behavioral tests. We have developed a simple, automated test of animal behaviors and will use the test to screen rapidly through thousands of candidate compounds and identify those with promise for treating nervous system disorders.